NVIDIA's Scalable Link Interface: The New SLI
by Derek Wilson on June 28, 2004 2:00 PM EST- Posted in
- GPUs
Final Words
In our conversation with NVIDIA, we noted that this technology should work with all software without any modification necessary, and NVIDIA was quoting numbers around 1.87x performance increase over a single card (under 3dmark '03). Of course, this may be an exception rather than the rule, and we do want to run our own tests (as impact will change over graphical complexity). Even more intriguing is the fact that NVIDIA talked about developers being able to take advantage of this technology in their games. It was indicated that, by doing so, games could see a linear (2x) performance increase. If realized, this would be unprecedented in real-world applications of this type of technology.In speaking about why multiple graphics card configurations haven't seen more light in the recent past, NVIDIA mentioned that the PCI bus was the limiting factor in being able to execute something like this on modern hardware. At this point, they still have an unbalanced bandwidth situation due to the x8 bandwidth limit on secondary x16 PCIe slots, but that's nothing like the difference between PCI and AGP (especially as full PCI bus bandwidth can't always be guaranteed to one device).
And then there's the problem of finding motherboards with multiple PCIe slots. The only one that we've seen so far is a multiprocessor board, which hasn't been released yet. To be fair, NVIDIA is targeting the system builders first, and won't be pushing a consumer SLI upgrade package until later (possibly this fall). The success or failure of this product will likely not rest on its technical merits, but rather on the availability of suitable motherboards, and the cost of the upgrade. We can see some hardcore gamers out there spending $500 on a card. We could see some even going so far as to upgrade their entire PC if it meant better performance. But it is hard for us to see very many people justifying spending $1000 on two NV45 based cards even for 2x the performance of one very fast GPU; perhaps if NVIDIA cripples some of its GPUs to work only as slaves and sells them for a (very) reduced price as an upgrade option. Even then, this isn't going to have as easy a time in the marketplace as the original 3dfx SLI solutions.
Now, what would really work in NVIDIA's favor is if they engineer their NV5x GPUs with backwards compatible SLI technology. Even the promise of such a thing might be enough to get some people to pick up an NV45 with the knowledge that their future upgrade would actually be an upgrade. For those who upgrade every generation, there would be a way to get more power for "free", and those who wait 2 or more generations to upgrade might have a new reason to take the plunge. This scenario is probably wishful thinking, but we can dream, can't we?
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Falloutboy525 - Tuesday, June 29, 2004 - link
acutally I wouldn't be surprised if one of the board manufactures puts 2 cores on one card. but man just thinking aboutt he physical size of the card gives me nightmares.Pumpkinierre - Tuesday, June 29, 2004 - link
The last of the SLI Voodoo2s had a dual gpu on a single board for one PCI slot. I cant see why the same couldnt be done for a dual 6800 gpu board on a single x16 PCIe slot which is nowhere near saturation with current gpus. Load balancing would be accomplished on board. In fact, they could do it on AGP 8x as well. They could extend this to multiple gpu (also possible on a 3x 16PCIe slot mobo (+ 3slot bridge) if it ever came out. Just think of the cooling with a Prescott cpu thrown in! Put a Vapochill to room temperature!Backward daisy chaining of components is a great idea but I doubt whether the greed of manufacturers will let it happen. The concept should not be limited to gpus but extend to mobo/cpus as well. A high speed link bus(Hypertransport perhaps, but not I2B) should allow systems to act as multiple processor system albeit with a little added latency. With parallel processing and multithreads around the corner, it would be useful to those who detest the enormous waste in the IT industry.
quanta - Tuesday, June 29, 2004 - link
Actually, NFactor, GeForce 6800's dedicated video codec is a step behind from ATI's videoshader. It adds transistor counts for things that can already be done by 3D core. As for power consumption goes, we only have NVIDIA's word for lower power requirement, but consider ATI also use videoshader for mobile parts, I suspect NVIDIA's claim only applies to NVIDIA's own products rather than ATI's.As for multiprocessing goes, ATI better catchup. After all, not every gamer can affort Evans & Sutherland simFUSION cards.
Phiro - Tuesday, June 29, 2004 - link
Yes, but there's the economy of scale. Nvidia has a "single" production line churning out the nv4x chipset and they package them accordingly to their price point - no major modifications required.The 6800U & x800XT don't really qualify as a "halo" products - they are a high-end version of the *same product the majority of users buy.
klah - Tuesday, June 29, 2004 - link
"And the whole "alienware sells 30k systems a year so there is a market for this" - 30k video cards a year is less than a drop in the bucket for the R&D spent on putting this together."The same could be said for the 6800U and x800XT. 99.9% of cards purchased will be sub-$200, so why bother with $500+ units? It's called a halo product. They are not built to make money. They are built for bragging rights and to generate a positive brand image. The 'buzz' this product creates for Nvidia is more substantial than spending the money on magazine ads and lan party sponsorships.
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"Excuse me, but I noticed that one 6800 Ultra takes two slots worth of airspace (due to the gigantic fan). So that means the Ultras would actually occupy the first and third PCIe slots"
No. All pci-e slots are not they same. This setup require two x16 slots. Dual x16 moptherboards do not have any other slots between these. These two slots have about double the space between them as the rest of the x8, x4 and x2 slots.
Nvidia is launching their nforce4 chipset later this year which will support dual pci-e x16. This is probably when this product will become available at retail.
Phiro - Tuesday, June 29, 2004 - link
Ugh what a dumb, dumb waste of technology. Give me dual video cards (for dual directx/opengl displays) but not SLI BS. This is far better served with multiple GPU's on the card, not multiple cards.If Nvidia is really so concerned with people being able to pay for the ultimate in performance or allowing people to "upgrade" without throwing everything away, Nvidia should go with a user manageable socket on their cards and support multi-core GPUs.
And the whole "alienware sells 30k systems a year so there is a market for this" - 30k video cards a year is less than a drop in the bucket for the R&D spent on putting this together.
If this idiotic SLI re-invention cost the release of the nv4x (and prolonged our nv3x agony) a single day, or increased the cost of the nv4x cards by a single dollar, Nvidia is once again crowned king of the dumbshits in my book.
Good choice buying 3dfx, Nvidia. It took a few years but Nvidia proved the old adage "You are what you eat". Nvidia's cards are hotter, larger, more complicated and more proprietary every day.
ScuZZee - Tuesday, June 29, 2004 - link
Excuse me, but I noticed that one 6800 Ultra takes two slots worth of airspace (due to the gigantic fan). So that means the Ultras would actually occupy the first and third PCIe slots (the second and fourth slot would be made useless since it would be blocked by the coolers).So does that means the mobo have to spaced out the two PCIe slots to accommodate the two Ultras?
SpeekinSfear - Tuesday, June 29, 2004 - link
barbaryJust FYI, if you're gonna buy two, the GT model which $399 instead of the $499 Ultra cost can do it too. They're smaller, less hot and power draining, and did I mention cost $100 less. I think the only power difference is that the GT ones have 50mhz less clock speed.
barbary - Tuesday, June 29, 2004 - link
So now I am stuck what to buy.I have a 670 Dell workstation and I was going to buy an ATI X800. But now should I buy a 6800 Ultra??
Question is do I buy two so I know I have a pair??
If I do and this technology doesn't come along for months I have wasted my money.
If I don't buy two a may never get a pair to match and have wasted my money.
Swaid - Tuesday, June 29, 2004 - link
Its not like you *have* to purchase 2 video cards for anything to work, thats only for the big spending enthusiast nuts and the CG/CAD guys. Its already part of the GPU, so its like an added bonus. The hard part in the beginning is getting a motherboard to support 2 PCIe x16.